An unauthorized program is defined as one that is not authorized by the authorized program facility (APF), not in supervisor state and does not have a system key (keys 0 through 7). An unauthorized program cannot communicate directly with the checkpoint data set. The unauthorized program can take checkpoints and do restarts, but after the operation has begun, a security interface is used by the system to prevent unauthorized alteration of the checkpoint data set.

If an unauthorized program tries to access a checkpoint data set directly, an error message appears, and the job terminates. In addition, the unauthorized program cannot take a checkpoint on a new checkpoint data set if another data control block (DCB) is already open to that data set.

Offline security of the checkpoint data set is ensured by the operator.